Method of coating can bodies



Aug. 15, 1939 E c. PFEFFER. JR

' METHOD OF COATING CAN BODIES 3 Sheets-Sheet 1 Filed NOV. 10, 1937 Ema?" Aug. 15,1939 E. c. PFEFFER, JR 2,169,316 I I IETHOD OF COATING CAN BODIES Filed Nov. 10, 1937' 3 Sheets-Sheet 2 Edward 4 g- 1939 E. c. PFEFFER, JR I 2,169,816

METHOD OF COATING CAN BODIES 3 Sheets-Sheet 3 Filed NOV. 10, 1937 Patented Aug. 15, 1939 UNITED STATES PATENT OFFICE METHOD OF COATING CAN BODIES Application November 10, 1937, Serial No. 173,938

2 Claims.

The invention relates generally to the art of coating can bodies and has for an object to provide a novel method of coating can bodies in a manner assuring against inadequate coatings at the can ends such as would be likely to break through and bare the metal of the can bodies during the double seaming of the can ends.

It is customary to interiorly coat metallic containers adapted to receive certain products, so that direct contact between said products and the metal of the containers is avoided. This is particularly true in the canning of beer, since it has been found that the slightest exposure of the tin forming the outer surface of the metal causes a chemical reaction upon the beer sufliclent to change its appearance, making it cloudy and unmarketable. I,

The protective coating has been applied in various ways, as by dipping, flushing, or flooding the inside, outside, or both inside and outside of the can bodies in the coating solution, usually lacquer or enamel, and this application is followed by a draining of surplus solution from the coated can bodies, the latter being accomplished by disposing the can bodies in a vertical or near vertical position. An example of this draining of surplus solution, following an application by the dipping method, is to be found in the application for Letters Patent filed by Alfred L. Kronquest, on April 12, 1937, Serial Number 136,473.

It has been found that when cans are thus permitted to drain off their surplus coating, the lowermost ends of the cans will retain a satisfactory coating film, but due to capillary action, or the surface tension of the draining coating material, the film at the upper extremity of the cans will become thin and inadequate, and during the double seaming of such cans faults appear at the inadequately coated ends which will expose bare metal portions to contact with the beer contained in such cans. Thus, in order to assure the provision of an adequate coating at that end of the cans from which coating material drains away, I have devised a method of coating in which the can is given the usual overall protective coating and also a supplementary or reinforce band coating at that end only from which the overall coating tends to drain away and thin out.

While the steps of the method may be reversed, it is preferred that the method shall comprise the steps of first forming at one extremity of the interior of a can a ,,cylindrical coating band of limited length, and thereafter forming on said can interior a complete surface coating.

More specifically the method comprises the steps of freely suspending cans with their axes disposed at an angle to the vertical and with one side only of the lower ends of the cans immersed in a protective coating bath, and rotating or rolling the cans along in the bath to provide cylindrical band coatings at said can ends, drying the band coatings, thereafter completely coating at least the interior surfaces of the cans, and permitting surplus coating to drain away while holding the band coated ends of the cans uppermost.

With the above and other objects in view which will more fully appear, the natureof the invention will be more clearly understood by following the description, the appended claims, and the several views illustrated in the accompanying drawings:

In the drawings:

Fig. 1 is a vertical cross section of an example of apparatus adapted for forming the cylindrical band coatings.

Fig. 2 is a front elevation of the apparatus shown in Fig. 1.

Fig. 3 is a side elevation of a can provided with a cylindrical band coating, a portion being broken away to show the interior of the can.

Fig.4 is a vertical cross section illustrating the complete or overall coating of. the interior of a band coated can by the spray method.

Fig. 5 is a vertical cross section illustrating a complete or overall coating of a can by the dipping method.

Fig. 6 is a vertical cross section illustrating the draining of a completely coated can.

Fig. 7 is a view similar to Fig. 3 and illustrates a finished can embodying both band coating and complete or overall coating.

In practicing my improved method the cans 5 are first given a cylindricalband coating 6 at that end only at which coating film is expected to drain away and thin out in a manner which ordinarily would result in an inadequate coating film at that point.

The cylindrical band coating may be formed internally only, but I prefer to apply the coating both inside and out, and while the coating can be applied by various forms of mechanism, including mere dipping or partial immersing equipments, I prefer to employ the apparatus disclosed in my copending application for Letters Patent, Serial Number 173,937, filed November 10, 1937. In this'apparatus the cans are freely suspended with their axes inclined to the vertical and with one side only of the lowermost ends of the cans immersed in a bath of protective coating material, and are rotated or rolled along in the bath to form the cylindrical band coating.

The apparatus of the patent application referred to includes a trough l of a length greater than the circumference of the cans and containing a constant level protective coating bath 8 therein. The cans are supported on trackage 9 with their axes inclined to the vertical and with one side only of the lowermost ends thereof immersed in the coating bath as shown in Figure 1. A power driven belt opposes the trackage 9 and engages the cans 5 thereon. The belt causes the cans to roll along the trackage with the result that a cylindrical band coating will be applied at the immersed end of the cans. By reason of the relation of the belt and trackage, and contact of the can flange with the upper edge portion of the trackage, the cans are held freely suspended in the bath, that is, out of contact with any portion of the trough proper. While it is preferred that the cans be rolled, or in other words given a movement of progression in addition to mere rotation, it should be understood that the band coating can be accomplished by mere rotation of the cans about stationary axes.

Upon completion of the cylindrical band coating the cans are air dried, or they may be baked. A band coated and dried can is shown in Figure 3 of the drawings. Although I prefer to coat the cans both internally and externally as shown and as previously described, it is to be understood that the invention comprehends the provision of internal coatings alone.

After the cans have been band coated and the coatings dried or hardened, they are given complete surface or overall coatings, internally alone or both internally and externally, by any approved method. In Figure 4 of the drawings I have illustrated the application of an internal overall coating by use of a spray Hi. In Figure 5 of the drawings I have illustrated the application of an internal and external overall coating by the dipping method as practiced by use of apparatus disclosed in the application for Letters Patent filed by Alfred L. Kronquest, on April 12, 1937, Serial Number 136,473. The apparatus referred to includes carriers II on which individual cans are supported and which are lowered and lifted by suitable mechanisms to immerse the cans in and remove them from the protective coating bath I2.

When the cans have received the desired overall coating the surplus of coating material is suitably drained therefrom in any approved manner. In Figure 6 of the drawings I have shown an example of means which may be employed during the draining step. The means shown is that disclosed in the Kronquest application above referred to and includes a travelling chain l3 with spaced can flange gripping clips It depending therefrom and serving to hold the cans while draining. Regardless of the means employed in the accomplishment of the surplus coating draining step of the method, the cans are always placed with the band coated ends thereof uppermost during the draining so that such thinning out of the overall coating as will occur will take place at the band coated extremity of the can without any danger of leaving the can with an inadequately coated portion which might break through during double seaming and leave bare metal portions exposed for contact with products to be contained in the can.

After application of the overall coatings the coatings are air dried or baked to suitably harden the protective coatings. A completed can is shown in Figure 7 of the drawings. This figure also illustrates the general position of the cans during the draining of surplus overall coating therefrom.

While it is preferred that the steps of the method should be performed in the order specifically described, it will be apparent that the broad purpose of the invention will be served if the superposed coatings are applied in reversed order, that is with the band coatings applied after instead of before the overall coatings. It is to be understood that any approved protective coating material may be used, enamel or lacquer being preferred.

What I claim is:

1. The process of coating cans to prevent double seaming faults which comprises suspending a can with one side only of the end at which the double seaming is to take place immersed in a coating bath, rotating said can to provide a relatively narrow band of coating on the immersed end of the can, drying the band coating, providing an overall coating interiorly of the can, and draining off surplus overall coating with the band coated end of the can uppermost during the draining.

2. The process of coating cans to prevent double seaming faults which comprises continuously and successively suspending a plurality of cans with their axes inclined to the vertical and with the ends only of the cans at which the double seaming is to take place partially immersed in a coating bath, rolling said cans while suspended as aforesaid to provide a relatively narrow band of coating on each can, drying the band coatings, applying an overall coating on the interior surfaces of the cans, and draining off surplus overall coating while the first mentioned ends are uppermost.

EDWARD C. PFEFFER, JR. 

